Piezoelectric actuators having piezoelectric ceramic layers stacked to form a multilayer stack are described in, e.g., German Patent Application No. DE 198 38 862 A 1. The piezoelectric ceramic layers have electrode layers, one electrode layer being provided between each of the piezoelectric ceramic layers, an outer cover layer being provided on each end face of the piezoelectric actuator and the piezoelectric ceramic layers and the outer cover layers each having a predetermined dielectric constant. The outer cover layers are passive layers of insulation and tolerance compensation and are made of unpolarized piezoceramic. The outer cover layers are machined to produce coplanar surfaces and have a greater layer thickness than the piezoelectric ceramic layers between the outer cover layers.
Piezoelectric actuators are advantageously triggered in cycles by a control unit at a high frequency. Due to the rapid switching operations, considerable electromagnetic interference is generated and must be reduced on the control unit or on the electric feeder lines to the piezoelectric actuators through complex measures. For example, interference suppression is achieved by using interference suppression chokes and/or interference suppression capacitors on plug connections, snubber networks on switching elements and switching flank limiting measures or shielded and/or twisted electric feeder lines to the piezoelectric actuators.